1. Field
The present disclosure relates generally to high temperature substrate materials, which may be used for making and/or depositing carbon nanotubes.
2. Technical Background
Carbon nanotubes are typically grown on substrate materials able to survive extreme conditions of manufacturing processes for carbon nanotubes, such as the substrate not softening at temperatures exceeding 800° C. and the substrate withstanding contact with potent chemicals, such as nitric acid used to etch or remove the carbon nanotubes. Accordingly, heat insensitive materials, such as gallium nitride, sapphire, silicon wafers, silica wafers hewn from bulk silica blocks, etc. are often used for the substrate materials. However, many conventional substrates for carbon nanotube growth and/or deposition tend to be inflexible, inefficiently shaped, thick and heavy, and extremely costly due to correspondingly extensive processes for manufacturing such substrates.
For example, typical silicon wafers 110, which may be used as substrates for carbon nanotube 112 growth, are grown as part of large crystal rods/ingots that are subsequently cut into disc-shaped wafers that are then finished with grinding, lapping, and polishing. These manufacturing steps result in circular wafers 110 with smooth finished surfaces 114, as shown in FIG. 1. However, the wafers 110 tend to be relatively thick and/or inflexible, because the cutting, grinding, lapping, and polishing manufacturing steps may be difficult with particularly thin flexible sheets. Further, inflexibility of conventional substrates may pose a problem for removal of carbon nanotubes 112 by making it difficult to scrape off and/or collect the carbon nanotubes 112. Further, a thermally grown oxide layer may be used to grow carbon nanotubes.
Further, Applicants have observed that wafer substrates 110 are circular, which may be inefficient for manufacturing carbon nanotubes, in terms of utilizing the available space, especially when the carbon nanotubes are manufactured in rectilinear spaces. However, due to the conventional crystal rod/ingot manufacturing approach, circular shapes tend to provide the maximum surface per slice of the rod, and cutting the circular shapes to rectilinear shapes may be counter-intuitive to substrate manufacturers due to the high expense of the manufacturing process and the desire of substrate manufacturers to maximize the surface area of the corresponding substrates, regardless of the shape of the equipment for manufacturing carbon nanotubes.
A need exists for substrates, such as those for use with making or using carbon nanotubes (e.g., growing, depositing, supporting, etc.), where the substrates overcome some or all of the above problems generally associated with conventional such substrates.